1. Field of the Invention
The present invention relates to a transfer belt unit mounted in an image forming device. In particular, the present invention relates to a mounting technique in which the transfer belt unit is inserted almost horizontally into and mounted in the image forming device.
2. Description of the Related Art
FIG. 5 is a schematic diagram for describing mounting of a conventional transfer belt unit in an image forming device. A transfer belt unit 200 has a substantially rectangular parallelepiped form, and a handle 35 (45) is placed on both of side surfaces near the center of the transfer belt unit where the weight of the transfer belt unit is balanced. When the transfer belt unit 200 is mounted in the image forming device, the transfer belt unit is inserted from the front surface of insertion of the transfer belt unit 200 to a unit inserting port 5 of the image forming device in a direction shown by an arrow DN. After the transfer belt unit 200 is moved to a normal position, the transfer belt unit is positioned (normally, fixed by being pressed down) at an operating position and is put into operation.
In the case described above, guide rails 60 and 70 having a cross-sectional surface of “U-shape” which extends from the unit inserting port 5 to inside are placed in the image forming device. The openings of the “U-shape” of the guide rails 60 and 70 are placed so that these openings face each other. On both of side surfaces of the transfer belt unit 200 near the front surface of the inserting direction and the rear surface of the inserting direction, positioning axes 31 and 41 and positioning axes 32 and 42 are placed, respectively. Therefore, insertion of the transfer belt unit 200 is carried out by putting the positioning axes 31, 32, 41, and 42 through the guide rails 60 and 70.
As described above, in the conventional transfer belt unit, when insertion and positioning of the transfer belt unit 200 are carried out, the transfer belt unit may fall out from the unit insertion port if the operator stops holding the transfer belt unit and releases the transfer belt unit from his or her hand in the insertion state as shown in FIG. 5, since there is nothing that holds the transfer belt unit near the rear surface in the inserting direction of the transfer belt unit and an orientation of the transfer belt unit is rotated to the direction of the arrow DF with the positioning axis 31 (41) as a rotational axis. For this reason, there has been a problem in an aspect of operability that the operator has to insert the transfer belt unit by taking into consideration an attitude of the transfer belt unit when the operator mounts the transfer belt unit in the image forming device.